1. Field of the Invention
This invention relates to arc welding and, more specifically, to electrode tip geometry for hollow electrodes used in a gas tungsten arc welding apparatus.
2. Background Art
Various gas tungsten arc welding apparatus are well known in the industry and find many applications. In general, the gas tungsten arc welding or GTAW apparatus comprises a non-consumable electrode and generally operates on direct current power applied to the electrode. During operation, an electric arc is formed between the working tip or face of the electrode and a metal workpiece. The electrode is often fabricated from tungsten or an alloy of tungsten in order to withstand the high temperatures inherent in the welding operation.
In the arc welding process, the relationship between electrode tip geometry and the arc stability has become increasingly important. It has, in the past, been the practice to control the area of electron emission for the arc by shaping the working tip of the electrode as a cone. The conical point may define a blunt or sharp tip; however, the conical point was generally formed as a sharp, 30.degree. to 120.degree. right circular cone.
A useful discussion of conical tip geometry may be found in Welding Research Supplement, "The Effect of Electrode Geometry in Gas Tungsten-Arc Welding", W. F. Savage et al, November 1965, pages 489-s to 496-s.
When using a hollow electrode with the GTAW process, the electrode tip cannot be shaped to a conical point because of the hole through the electrode. In addition, a small amount of inert gas flows through the hollow electrode. Both of these facts have a negative affect on arc stability and control.
In view of the foregoing, it would be a significant advancement in the art of gas tungsten arc welding with hollow electrodes to provide an electrode having a tip design configured to emit a controlled and stable arc.